Objective:To investigate the influence of histone deacetylase inhibitor（Trichostatin A）to multiplication

invasion

cell cycle of breast cancer MDA-MB-231 cell line.Methods:After 6-48hours treatment with the concentration（100～400nmol/L）of Trichostatin

the growth activity of MDA-MB-231 cell line was detected by MTT.The expression of ERα

MMP-9 mRNA was detected by RT-PCR with different concentration（100～400nmal/L TSA）during 24 hours to MDA-MB-231 cell line.The expression of ERα

MMP-9 protein was examined by immunohistochemistry with different concentration（100～400nmol/L TSA）during 24 hours treatment to MDA-MB-231 cell line.With cell invasion experiment to detect the change of invasive power by using different concentration（100～400nmol/L TSA）during 24 hours to MDA-MB-231 cell line.Results: Trichostatin can inhibit the growth of MDA-MB-231 cell line

which was time and dose dependent.Trichostatin can delay the cell cycle G

2

/M stage

stop the cell stage in G

2

stage.Trichostatin can up-regulate the expression of ERαmRNA

down-regulate the expression of MMP-9 mRNA in cells.The invasion experiment indicate that Trichostatin can conspicuous inhibit the invasion of MDA-MB-231 cell line.Conclusions:Trichostatin can inhibit the accrementition

invasion and metastasis of MDA-MB-231 cell line evidently

and one of the mechanism may be the up-regulation of ERαand the down-regulation of MMP-9.